With the widespread of digital image photographing apparatuses such as digital still cameras and mobile phones having a camera function, recording media for recording photographed images such as hard discs have been distributed inexpensively.
Generally, users of digital image photographing apparatuses and the like store photographed images in a recording medium such as a hard disc with a large capacity.
The users have difficulty searching a large amount of stored images for a desired image. For this reason, images are classified into categories in order to allow the user to easily perform image search.
As an image classification art, there has been known an art of extracting a feature from each of stored images and classifying each of the images into a classification destination with use of the extracted feature, as disclosed in Patent Literatures 1 and 2 for example.